The overall objective of the Clinical Core is to provide human specimens for the studies described in Research Projects 1-3. These specimens will supplement the existing extensive collection of unique banked specimens that are being used and accrued in the current CCHI. Note: the core will only obtain human specimens from subjects who are receiving the standard-of-care (e.g., vaccinated with the Ty21a typhoid vaccine because of travel to endemic areas or work in microbiology labs, or undergoing medically-indicated colonoscopies) and do not involve off-label interventions. The goals of this core will be achieved through the following specific aims.